Pulmonary shunt measurement was compared using the standard oxygen (Berggren) technique and a new multiple inert gas infusion (Wagner et al.) technique in 11 mongrel dogs with either regional atelectasis or diffuse pulmonary edema. Relative retentions of sulfur hexafluoride, ethane, cyclopropane, halothane, diethyl ether, and acetone were used to calculate intrapulmonary shunt. Relative dilution of oxygen (Berggren method) was used to calculate total right to left shunt. The two methods gave similar results in the range of 20–80%. At low shunts the oxygen method measured higher values. This is because of the greater relative importance of fixed extrapulmonary shunts at this level and, as well, error in the measurement of PO2. Both techniques are suitable for normal clinical use.